1. Field of the Invention
The present invention provides an apparatus comprising a photomask holder for holding a photomask, which is placed in the transfer box and is suitable for photolithography process. The photomask is disposed on the long cambered surface of the protrusion disposed in the photomask holder so that the friction between the protrusions and the Chromium (Cr) deposition formed on the bottom surface of the photomask can be effectively prevented. Thus, generation of particulates can be effectively prevented.
2. Description of the Related Art
Heretofore, a conventional holder 10 of a photomask 201 (as illustrated in FIGS. 1 & 2) is placed in a base 20 of a transfer box. The holder 10 is U-shaped and comprises pluralities of falciform members 101 and protrusions 102. The holder 10 is made of plastic material and is formed as a one-piece structure via injection molding process, and the protrusion 102 is adopted to support the photomask 201. As the surface contact area of the protrusion 102 with the photomask 201 is rather large and since the protrusion 102 is made of a plastic material, the protrusion 102 is not strong enough to resist friction with the photomask 201. Frequently, during inspection, the position of the photomask 201 on holder 10 is adjusted or lifted-off and placed back on the holder 10, and the protrusion 102 will be subjected to friction with the photomask 201 with Chromium (Cr) formed on the bottom surface of the photomask 201, which serves as a circuit protecting shroud layer, and thereby generate particulates. Wherein the Chromium (Cr) deposition on the bottom surface of the photomask 201 is jointed with a jacket membrane 201a to protect the photomask 201 from the dust, which would otherwise adversely affect the focus of the photomask 201. If the surface of the jacket membrane 201a is adhered with a lot of dust or particulates, the jacket membrane 201a must be replaced in order to prevent the wafer from inaccurate exposure. However, the cost of the jacket membrane 201a is high and therefore the overall cost is increased.
FIGS. 1, 2 and 3 respectively, are a perspective view, a front sectional view and a testing waveform chart of the photomask holder. The friction between the protrusion 101 and the photomask 201 would generate particulates, thus the surface of the photomask 201 on the surface of the protrusion 101 is rendered uneven. Thus, it is essential to repeatedly adjust the position of sucking disk to correspond with the photomask 201 to allow the robotic arm uses sucking disk to properly hold and adjust the position of the photomask 201 in the clean room. If the position of the sucking disk of the robotic arm is not adjusted properly, the sucking disk cannot suck the photomask 201 to move. During the inspection process, the protrusion 101 may get seriously damage to produce the particulates generated due to the abrasion of the protrusion 101. And, the testing waveform chart presents some pulsations with big amplitudes and affects the movement of the photomask 201.
Moreover, the transfer box is adopted to protect the photomask 201 from dust in order to ensure that the photomask 201 is clean. Thus, this increases the cost and incurs extra labor attributed to periodic cleansing.